An instant messaging service provides the end users a means for fast, interactive, mainly text-based communication. It includes both the Internet or SMS-style messaging with short, textual messages and also related value added services, such as presence management and chat room-type scenarios.
In general, presence can be considered containing various dynamic information of a user accessing the service via different means. Examples of this information are the reachability and availability of the user for communication and other, more emotional status such as mood and willingness for communication.
The retrieval and authorization of presence information has been solved in the Internet-based instant messaging solution in a proprietary way. The user is identified by his/her user name. Since the known and most prevalent IM system is based on access from personal desktop computers, the identification of the PC is not important; the IP-address of the PC is used only for internal routing purposes. In mobile instant messaging, the identification of the particular IM application might become more important: the user may conceivably access the service from multiple devices at the same time and some of the status information, e.g., reachability and capabilities might not best be tied to the user but rather to the particular IM application.
There is moreover a need to define a protocol using an open architecture so that various vendors can begin to offer such services.